The present invention relates to a process and an apparatus for reprocessing polyurethane foam wastes, and in particular, flexible foam wastes, for recycling as an additive in the production of polyurethane from polyol and isocyanate, wherein the wastes are first comminuted coarsely, the particles obtained are mixed with one of the reaction components, and the latter mixture undergoes fine comminution. A similar process is described in German Auslegeschrift 2,339,752 (which corresponds to British Patent 1,435,210)
From German DE-B 4,025,102 it is also known to comminute polyurethane foam waste to a particle size below 10 mm, with re-use after mixing with foam-forming one-component prepolymers.
Polyurethane foam wastes arise, for example, during polyurethane foam trimming and also during foam molding as a result of escape of the product from the vents and in the plane of the parting line. Such wastes are reprocessable and can be recycled in some fields of application, recycling can take place only when the wastes are comminuted finely, that is to say, are in powder form. Coarse comminution presents no problems and is achieved, for example, by chopping, crushing or grinding. According to the above noted '752 publication, fine comminution can be attained by wet grinding. This involves considerable plant cost and high energy requirements. Dry grinding has also been used for fine comminution of foam waste with an energy requirement of from 0.15 to 0.2 kWh/kg, being more favorable than the wet grinding process. However, plant cost is again very high bemuse of considerable dust formation.
The object of the present invention was therefore to carry out a low-dust, fine comminution with a lower plant cost and lower energy cost.